Coated granular fertilizers, methods of manufacture thereof, and uses thereof

ABSTRACT

A coated fertilizer comprising a fertilizer granule and a coating disposed on a surface of the fertilizer granule, wherein the coating comprises interpenetrating domains comprising polymer domains and wax domains. A method of making the coated fertilizer is also disclosed.

BACKGROUND

Granular fertilizers can be coated to reduce dust production and to slowthe release of nutrients into the soil. To improve fertilizer uptake bythe plant, the available fertilizer concentration in the soil shouldmatch the plant growth need. Since plants typically follow a sigmoidalgrowth pattern, the fertilizer availability should be similar to theplant growth rate. Due to various parameters such as soil erosion,volatilization of ammonia, and leaching of nitrates, only about 40% ofcurrently available fertilizers like urea are absorbed by the plant andthe remainder is lost to the environment. Hence, there remains a need inthe art for improved coated fertilizer which allows for a higherutilization of the fertilizer by the plant.

SUMMARY

Described herein is a coated fertilizer comprising a fertilizer granuleand a coating disposed on a surface of the fertilizer granule, whereinthe coating comprises interpenetrating domains comprising polymerdomains and wax domains.

A process of manufacturing the coated fertilizer comprises at leastpartially dissolving a polymer and a wax in an organic solvent to form acoating composition; contacting the coating composition with a pluralityof fertilizer granules to form at least partially coated fertilizergranules; evaporating the organic solvent from the at least partiallycoated fertilizer granules to form dried at least partially coatedfertilizer granules; and heating the dried at least partially coatedfertilizer granules at a temperature effective to at least partiallymelt the wax to form a coating comprising interpenetrating domainscomprising polymer domains and wax domains.

Alternatively, a process of manufacturing the coated fertilizercomprises at least partially dissolving a first structural polymer in afirst solvent having a first boiling point to form a first solution; atleast partially dissolving a second polymer and a wax in a secondsolvent having a second boiling point to form a second solution, whereinthe second boiling point is different from the first boiling point;contacting the first solution and the second solution with a pluralityof fertilizer granules to form at least partially coated fertilizergranules; evaporating the first solvent and the second solvent from theat least partially coated fertilizer granules to form dried at leastpartially coated fertilizer granules; and heating the dried at leastpartially coated fertilizer granules at a temperature effective to atleast partially melt the wax to form a coating comprisinginterpenetrating domains comprising polymer domains and wax domains.

The above described and other features are further set forth in thefollowing figures, detailed description, and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The following is a brief description of the drawings wherein likeelements are numbered alike and which are presented for the purposes ofillustrating the exemplary embodiments disclosed herein and not for thepurposes of limiting the same.

FIG. 1A is a scanning electron microscopic image of a sample at 500times magnification with no pre-treatment.

FIG. 1B is a scanning electron microscopic image of the sample of FIG.1A at 2000 times magnification with no pre-treatment.

FIG. 2A is a scanning electron microscopic image of a sample at 500times magnification with 5 hours of pre-treatment.

FIG. 2B is a scanning electron microscopic image of the sample of FIG.2A at 2000 times magnification with 5 hours of pre-treatment.

FIG. 3A is a scanning electron microscopic image of a sample at 500times magnification with 10 hours of pre-treatment.

FIG. 3B is a scanning electron microscopic image of the sample of FIG.3A at 2000 times magnification with 10 hours of pre-treatment.

FIG. 4A is a scanning electron microscopic image of a sample at 500times magnification with 15 hours of pre-treatment.

FIG. 4B is a scanning electron microscopic image of the sample of FIG.4A at 2000 times magnification with 15 hours of pre-treatment.

DETAILED DESCRIPTION

The coated fertilizer comprising a fertilizer granule and a coatingcomprising interpenetrating domains of polymer domains and wax domainshas a release rate which more closely matches plant growth rate and as aresult has a higher utilization rate than coated fertilizer without theinterpenetrating domains. Interpenetrating domains, as used herein,describe domains of different materials which penetrate each othermutually creating a morphology demonstrating distinct domains ofseparate materials which border one or more domains of a differentmaterial. These domains may be irregular in shape. A useful visualanalogy is puzzle pieces in which adjoining pieces are domains formedfrom different materials. Without being bound by theory it is believedthat when the polymer is applied it forms a non-continuous coating ofpolymer domains on the granules and at least some of the gaps in thepolymer domains are filled with wax domains when the wax is applied.

The embodiments described herein relate to a coated fertilizer granule.The coating comprises interpenetrating domains of at least one polymerand at least one wax. The fertilizer granule is at least partiallycoated with a coating that comprises interpenetrating domains of atleast one polymer and at least one wax.

It is desirable to improve the mechanical strength of the at leastpartially coated fertilizer granules. Mechanical strength can affect theability of the fertilizer granules to withstand the normal handlingprocedures and can increase the effectiveness of the coating. It hassurprisingly been discovered that pre-treating a surface of thefertilizer granule before applying the coating can improve themechanical properties of the at least partially coated fertilizergranules as well as can improve the adherence of the coating to thefertilizer granule. The pre-treating, among other things, can includesmoothing a surface of the fertilizer granule. The pre-treatment canoccur after the fertilizer granule has been formed. Coated fertilizerscontaining a pre-treated fertilizer granule can have a significantlylower percent nitrogen release after 7 days as compared to coatedfertilizers not containing a pre-treated fertilizer granule. Forexample, the pre-treated fertilizer granule can have a percent nitrogenrelease after 7 days of less than or equal to 70%, for example, lessthan or equal to 65%, for example, less than or equal to 60%.Pre-treatment can include smoothing of the fertilizer granule surface bypre-heating the granule to a temperature greater than or equal to 90° C.For example, the temperature can be greater than or equal to 100° C.,for example, greater than or equal to 105° C., for example, greater thanor equal to 125° C. The pre-treatment time can be greater than or equalto 5 hours, for example, greater than or equal to 10 hours, for example,greater than or equal to 15 hours, for example, greater than or equal to20 hours.

After a coating has been applied (e.g. a 2% coating), the coatedfertilizer containing the pre-treated fertilizer granule can bepost-treated and weight loss measured. The 2% coating generally refersto a 2% polymer coating by weight. The coating can be applied by theprocesses described herein and gives a control sample allowingobservation of the effect of the pre-treatment. Weight loss can be lessfor coated fertilizers containing the pre-treated fertilizer granule ascompared to coated fertilizers not containing the pre-treated fertilizergranule. Post-treatment can include heating the pre-treated, at leastpartially coated granules at various temperatures and then measuringpercent weight loss. Heating can include temperatures greater than orequal to 50° C., for example, greater than or equal to 60° C., forexample, greater than or equal to 70° C., for example, greater than orequal to 80° C., for example, greater than or equal to 90° C., forexample, greater than or equal to 100° C. The post-treatment heatingtime can be greater than or equal to 5 hours, for example, greater thanor equal to 10 hours, for example, greater than or equal to 15 hours,for example, greater than or equal to 20 hours. The coated fertilizercontaining the pre-treated fertilizer granule can have a percent weightloss of less than or equal to 0.20% after post-treatment, for example,less than or equal to 0.15%, for example, less than or equal to 0.10%.

The fertilizer granules can comprise nitrogen, phosphorus, or potassiumsources such as ammonium nitrate, ammonium sulfate, ammonium sulfatenitrate, calcium nitrate, calcium ammonium nitrate, urea,urea-formaldehyde, monoammonium phosphate (“MAP”), diammonium phosphate,polyphosphate compounds, phosphate rock, single superphosphate (“SSP”),triple super phosphate, potassium nitrate, potassium chloride, potassiumsulfate (“SOP” or potash), or a combination comprising at least one ofthe foregoing. In some embodiments, the fertilizer granules compriseurea. The amounts of nitrogen, phosphorus, or potassium sources includedin the final fertilizer granules depends on the intended end use, andcan be 0 to 60 wt. % for each component, based on the total weight ofthe fertilizer granule.

Additionally, magnesium sulfate and a source of one or more traceelements, i.e., micronutrients can be included, for example boron,calcium, chlorine, cobalt, copper, iron, manganese, molybdenum, nickel,sodium, zinc, or a combination comprising at least one of the foregoingcan be present. These nutrients may be supplied in elemental form or inthe form of salts, for example as sulfates, nitrates, or halides. Theamount of plant micronutrients depends on the intended end use and canbe, for example, 0.1 to 5 weight percent (wt. %), based on the totalweight of the fertilizer granule.

Fillers can further be present in the granule, for example bentonite,calcite, calcium oxide, calcium sulfate (anhydrous or hemihydrate),dolomite, talc, sand, or a combination comprising at least one of theforegoing fillers.

Other components of granular fertilizers can include, for example,surfactants, nucleation agents, or recycled fertilizer particles, whichcan act as a source of nucleating agents, nucleating soil conditionerssuch as calcium carbonate, activated carbon, elemental sulfur, biocidessuch as pesticides, herbicides, or fungicides, wicking agents, wettingagents, heat stabilizers, adhesives such as cellulose, polyvinylalcohols, fats, oils, gum arabics, vinylidene ultraviolet stabilizers,antioxidants, reducing agents, colorants, binders (i.e.,organochlorides, zeins, gelatins, chitosan, polyethylene oxide polymers,and acrylamide polymers and copolymers), and the like, as well ascombinations comprising at least one of the foregoing.

The fertilizer granules can have any shape or size desired for theirintended use. In some embodiments the fertilizer granules aresubstantially spherical. The fertilizer granules have an averageparticle diameter of 1.0 to 4.0 millimeters (mm). Within this range theaverage particle diameter can be greater than or equal to 1.5, orgreater than or equal to 2.0 mm. Also within this range the averageparticle diameter can be less than or equal to 3.5, or less than orequal to 3.0 mm. In some embodiments at least 90% by weight of thefertilizer granules have a particle diameter of 2.0 to 4.0 mm Particlediameter is determined according to “Size Analysis—Sieve Method” IFDCS-107 issued by International Fertilizer Development Center (IFDC) whichis the most common and internationally approved method used to determinefertilizer particle size.

The coating on the fertilizer granule comprises interpenetrating domainscomprising polymer domains and wax domains. The polymer domains have arate of biodegradation which differs from the rate of biodegradation ofthe wax domains when subjected to the same conditions. When the polymerdomains comprise two or more polymers, each polymer has a different rateof biodegradation when subjected to the same conditions.

In some embodiments the polymer domains comprise a biopolymer. Exemplarypolymers include polysaccharides, polyesters, lignin, and combinationscomprising at least one of the foregoing. Exemplary polysaccharidesinclude cellulose acetate, cellulose triacetate, starch acetate, or acombination comprising at least one of the foregoing. Exemplarypolyesters include poly(butylene succinate), poly(butylene adipateterephthalate), poly(lactic acid), poly(lactic acid-co-glycolic acid),poly(butylene succinate), poly(caprolactone), poly(glycolide),poly(hydroxybutyrate), poly(hydroxybutyrate-co-hydroxy valerate), or acombination comprising at least one of the foregoing.

The cellulose acetate can have a weight average molecular weight (M_(w))of 25,000 to 120,000 grams per mol (g/mol), for example, 35,000 to70,000 g/mol.

The cellulose triacetate can have a M_(w) of 100,000 to 350,000 g/mol,for example, 125,000 to 300,000 g/mol, for example, 200,000 to 275,000g/mol.

Starch acetate is a starch that has been acetylated to a degree ofsubstitution (DS) of 1 to 3 with an acetyl value of 20% to 70%. As usedherein, “acetyl value” refers to the weight percent (wt %) of aceticacid per unit measure of starch acetate. For example, an acetyl value ofapproximately 62.5 is equivalent to a DS of 3.0.

The poly(butylene succinate) (PBS) can have a M_(w) of 70,000 to 160,000g/mol. In some embodiments the poly(butylene succinate) can have anM_(w) of 100,000 to 150000 g/mol, for example, 120,000 to 140,000 g/mol.In some embodiments the poly(butylene succinate) can have a M_(w) of75,000 to 125,000 g/mol, for example, 90,000 to 110,000 g/mol.

The poly(butylene adipate-terephthalate) (ECOFLEX™) can have a weightaverage molecular weight (M_(w)) of 30,000 to 120,000 g/mol, forexample, 50,000 to 100,000 g/mol.

The poly(lactic acid) (PLA) can have a weight average molecular weight(M_(w)) of 30,000 to 250,000 g/mol. The PLA can comprise recycled PLA,scrap PLA or a combination comprising at least one of the foregoing. Insome embodiments the poly(lactic acid) can have a M_(w) of 150,000 to210,000 g/mol, for example, 175,000 to 190,000 g/mol. In someembodiments the poly(lactic acid) can have a M_(w) of 30,000 to 70,000g/mol, for example, 40,000 to 65,000 g/mol.

The poly(lactic acid-co-glycolic acid) can have a M_(w) of 5,000 to300,000 g/mol, for example, 10,000 to 250,000 g/mol, for example, 40,000to 150,000 g/mol.

The poly(caprolactone) can have a M_(w) of 500 to 80,000 g/mol, forexample, 5,000 to 70,000 g/mol, for example, 15,000 to 60,000 g/mol.

The poly(glycolide) can have a M_(w) of 500 to 60,000 g/mol, forexample, 5,000 to 50,000 g/mol, for example, 20,000 to 40,000 g/mol.

The poly(hydroxybutyrate) can have a M_(w) of 10,000 to 500,000 g/mol,for example, 30,000 to 400,000 g/mol, for example, 75,000 to 350,000g/mol.

The poly(hydroxybutyrate-co-hydroxy valerate) can have a M_(w) of 10,000to 600,000 g/mol, for example, 30,000 to 500,000 g/mol, for example,100,000 to 400,000 g/mol.

Lignin is a polymer of aromatic alcohols most commonly derived fromwood. Lignin can be obtained by the Kraft process. Exemplary ligninincludes Kraft lignin marketed under the name of INDULIN™ AT orPROTOBIND™ 1000.

In some embodiments, the polymer domains comprise at least two polymers.These polymers may be miscible so as to form a single domain together ormay be immiscible and form separate polymer domains.

The coating comprises polymer domains in an amount of 50 to 80 wt %,based on the total weight of the coating.

The wax domains comprise a C₅-C₃₅ wax, polyethylene wax, mineral wax,biobased wax, shellac, or a combination comprising at least one of theforegoing. Waxes are liquid at 110 to 200° F. (43 to 95° C.). Exemplarywaxes include natural petroleum waxes, including paraffin waxes (hard,crystalline, brittle waxes composed primarily of unbranched alkanes,typically having melting points of 48 to 70° C.), microcrystalline waxes(soft, amorphous, malleable waxes composed primarily of branchedalkanes, typically having melting points of 54 to 95° C.), and fullyrefined paraffin waxes. Synthetic waxes can also be used, includingpolyethylene waxes having, for example, a degree of polymerization of 10to 18 carbon atoms. Exemplary waxes that are commercially availableinclude a petroleum wax, C30+ from Chevron Phillips Chemical (CP-Chem),7089A, R-4408, and R-3053A available from International Group, Inc.

The coating comprises wax domains in an amount of 20 to 50 wt %, basedon the total weight of the coating.

When coated on the fertilizer granules, the amount of the coating isless than or equal to 6 wt. %, for example, 0.1 to 6 wt. %, 0.5 to 5 wt.%, 2 to 5 wt. %, or 3 to 5 wt. %, based on the total weight of thecoated fertilizer.

In any of the foregoing embodiments, the coatings can further comprisean adjuvant as known in the art, for example a colorant, an adhesionpromoter, or a surfactant, provided that the adjuvant does notsignificantly adversely affect the desired properties of the coatedfertilizer. For example, a surfactant can include a primary andsecondary (C₁₆₋₃₀)alkylamine, a (C₁₆₋₃₀)fatty acid amide of a primary(C₁₆₋₃₀)alkylamine, or a (C₁₆₋₃₀)fatty acid ester of a (C₁₆₋₃₀)alkanol.Examples of the foregoing surfactants include cetyl amine, stearylamine, arachidyl amine, behenyl amine, dicetyl amine, distearyl amine,diarachidyl amine, dibehenyl amine, di(hydrogenated tallow) amine, cetylstearamide, stearyl stearamide, stearyl erucamide, erucyl erucamide.

Further, in any of the foregoing embodiments, the coating is disposeddirectly on the granule or other layers, that is, no intervening layersare present other than those described. The coating can be continuous ordiscontinuous. To optimize the sustained release features of the coatedfertilizer, the coating covers 90 to 100% of the surface area of thefertilizer granule.

The thickness of the coating is adjusted to provide the desiredsustained release and protection properties. In some embodiments, thetotal thickness of the coating is 20 to 70 micrometers. For example, thethickness can be greater than or equal to 25, or greater than or equalto 30 micrometers. For example, the thickness can be less than or equalto 65, or less than or equal to 60 micrometers.

A process of manufacturing the coated fertilizer comprises at leastpartially dissolving a polymer and a wax in an organic solvent to form acoating composition; contacting the coating composition with a pluralityof fertilizer granules to form at least partially coated fertilizergranules; evaporating the organic solvent from the at least partiallycoated fertilizer granules to form dried at least partially coatedfertilizer granules; and heating the dried at least partially coatedfertilizer granules at a temperature effective to at least partiallymelt the wax to form a coating comprising interpenetrating domainscomprising polymer domains and wax domains. The temperature effective toat least partially melt the wax can be 30° C. to 130° C. Additional waxmay be applied during heating. The coating composition may furthercomprise an additional polymer. It is further contemplated that anadditional coating composition may be used to at least partially coatthe plurality of fertilizer granules. The additional coating compositionmay be applied simultaneously or sequentially with the coatingcomposition. The additional coating composition may comprise the samecomponents as the coating composition but in different amounts or theadditional coating composition may comprise only a part of thecomponents found in the coating composition. The term “at leastpartially dissolving” is inclusive of suspending a material in asolvent. It is also inclusive of forming an emulsion.

The process can further include pre-treating the fertilizer granulebefore the coating is applied. Pre-treating the fertilizer granule canassist in providing greater adherence of the coating to the fertilizergranule and in improving the ability of the coated fertilizer towithstand post formation tests as previously described herein.Pre-treating the fertilizer granule can include smoothing the surface ofthe fertilizer granule.

Smoothing the plurality of fertilizer granules can be achieved byheating, e.g., heating in a rotating drum or fluid bed. It is furthercontemplated that mechanical methods such as ball milling could also beused to smooth the plurality of fertilizer granules. In an exemplarymethod, a plurality of fertilizer granules are heated to a temperaturegreater than or equal to 90° C. for less than or equal to 15 hours. Thetemperature can be less than or equal to 110° C. For example, thetemperature can be 90° C. to 100° C., or 100° C. to 110° C. The time canbe 1 hour to 5 hours, or 5 hours to 15 hours. The fertilizer granulescan be heated in an oven, a forced air oven, disc dryer, paddle dryer,rotary dryer, conveyor dryer, fluid bed dryer, or a combinationcomprising at least one of the foregoing. Optionally, the fertilizergranules can be cooled before coating.

Contacting the coating composition with a plurality of fertilizergranules can be achieved by spray coating (for example, top, bottom, orside spray coating), drum coating, pan coating, fluid bed coating,continuous pour coating, or any other method known to those of skill inthe art. This coating can be done in a batch or in a continuous process.The granules can be coated with a single layer in a single coatingapplication, or the granules can be coated with multiple layers of thesame coating material, such as, 2, 3, 4, 5, or more layers. Evaporatingand heating the at least partially coated fertilizer granules can occurin the same step or in sequential steps. Exemplary devices include arotary evaporator, an oven, or the like.

Exemplary organic solvents include chloroform, toluene, methylenechloride, or a combination comprising one or more of the foregoing.

Alternatively, a process of manufacturing the coated fertilizercomprises at least partially dissolving a first polymer in a firstsolvent having a first boiling point to form a first solution; at leastpartially dissolving a second polymer and a wax in a second solventhaving a second boiling point to form a second solution, wherein thesecond boiling point is different from the first boiling point;contacting the first solution and the second solution with a pluralityof fertilizer granules to form at least partially coated fertilizergranules; evaporating the first solvent and the second solvent from theat least partially coated fertilizer granules to form dried at leastpartially coated fertilizer granules; and heating the dried at leastpartially coated fertilizer granules at a temperature effective to atleast partially melt the wax to form a coating comprisinginterpenetrating domains comprising polymer domains and wax domains. Thetemperature effective to at least partially melt the wax is in the rangeof 30° C. to 130° C. Additional wax may be applied during heating.Contacting the coating composition with a plurality of fertilizergranules can be achieved by spray coating (for example, top, bottom, orside spray coating), drum coating, pan coating, fluid bed coating,continuous pour coating, or any other method known to those of skill inthe art. This coating can be done in a batch or in a continuous process.The granules can be coated with a single layer in a single coatingapplication, or the granules can be coated with multiple layers of thesame coating material, such as, 2, 3, 4, 5, or more layers. Evaporatingand heating the at least partially coated fertilizer granules can occurin the same step or in sequential steps. Exemplary devices include arotary evaporator, an oven, or the like.

The process can further include pre-treating the fertilizer granulebefore the first solution and the second solution are contacted with thefertilizer granule. Pre-treating the fertilizer granule can assist inproviding greater adherence of the first solution and/or the secondsolution to the fertilizer granule and in improving the ability of thecoated fertilizer to withstand post formation tests as previouslydescribed herein. Pre-treating the fertilizer granule can includesmoothing the surface of the fertilizer granule.

It is also contemplated that the coated fertilizer described herein maybe mixed with uncoated fertilizer granules or with a coated fertilizerhaving a coating comprising a polymer but free of wax.

In use, the coated fertilizer is applied to the locus of a plant orseed, in particular the soil of a plant or seed to be fertilized.

The coated fertilizers having sustained release properties are furtherillustrated by the following non-limiting examples.

EXAMPLES Example 1

The materials used in Example 1 are described in Table 1.

TABLE 1 Component Chemical Description Source PBS A Poly(butylenesuccinate) 18127 Danimer PBS B Poly(butylene succinate) 1020MD ShowaDenko PLA Poly(lactic acid) 2003D Natureworks C30+ Alpha-olefin waxChevron Phillips Chloroform Aldrich Methylene Aldrich Chloride TolueneAldrich

General Procedures

Urea granulation. In urea granulation, seed particles, or recycled ureaprills, are rotated through a central agglomeration tube via a highvelocity air stream. A spray nozzle at the bottom of the agglomerationtube sprays urea melt onto the particles. Because the urea melt dropletsare supplied at high velocities with air constantly passing through thegranulator, the seeds are wetted and dried efficiently. As more ureamelt is supplied by the spray nozzles, the urea particles grow indiameter and the process is concluded when the desired size has beenachieved.

Preparation of coating formulations. Coating solutions were made usingthe formulations shown in Table 2 and Table 3. In Tables 2 and 3, “g” isthe abbreviation for grams.

Coating procedure. The coating solutions were applied to the fertilizergranules using an air atomized spray in a rotating drum. For theexamples in Table 2 additional C30+wax was melted and applied to thepartially coated particles using a rotary evaporator rotating at 20-30revolutions per minute (rpm) in an oil bath. For the examples in Table3, all the wax was applied using the solutions which were applied usingan air atomized spray. The examples in Table 3 were further subjected tothermal conditioning using either a rotary evaporator at a temperatureof 95-101° C. for 20 minutes, or maintained in a 70° C. oven for 1 or 2hours.

Urea release test. The test is used to mimic a release profile of ureaat given time intervals. The time intervals that samples were taken andanalyzed were 24 hours, 7 days, and 14 days. 5 grams of coated granuleswere placed in 95 grams of deionized water at room temperature for thespecified time period. The water was analyzed for nitrogen content atthe end of the time period, measured in percent. The urea release testgives information allowing for a calculation of how much urea is nolonger bound by the coating. In Table 2, in Sample 1, 31.8% of theinitial amount of coated urea used in the test has been released in 7days. Stated another way Sample 1 demonstrates that about 70% of theurea was still entrapped by the coating (after 7 days) and graduallydiffusing.

TABLE 2 24 h N 7 day N 14 day N Sample # Solution 1 Solution 2 Rotovaprelease release release 1 9 g PBS A, 21 g 21 g PBS A, 9 g 0.25 g 5.331.8 — PLA, in 900 g PLA, 30 g C30+, in C30+ methylene 900 g methylenechloride chloride 2 9 g PBS B, 21 g 21 g PBS B, 9 g 0.37 g 0 11.9 — PLA,in 900 g PLA, 22.5 C30+, C30+ methylene in 900 g methylene chloridechloride 3 9 g PBS A, 21 g 21 g PBS A, 9 g 0.37 g 0.52 3.17 7.92 PLA, in720 g PLA, 22.5 g C30+, C30+ methylene in 650 g methylene chloride andchloride, 250 g 180 g toluene toluene 4 9 g PBS A, 21 g 21 g PBS A, 9 g 0.5 g 0.13 1.0 — PLA, in 720 g PLA, 15 g C30+, in C30+ methylene 650 gmethylene chloride, 180 g chloride, 250 g toluene toluene 5 9 g PBS A,21 g 21 g PBS A, 9 g 0.37 g 0.06 1.38 4.09 PLA, in 720 g PLA, 22.5 gC30+, C30+ methylene in 650 g methylene chloride, 180 g chloride, 250 gtoluene toluene

TABLE 3 24 h N 24 h N release release 24 h N after after 24 h N releaseoven at oven at release before after 70° C. for 70° C. for Sample #Solution 1 Solution 2 conditioning Rotovap 1 hour 2 hours 6 9 g PBS A, 9g PBS A, 43.5 37.4 17.9 5.98 21 g PLA, 21 g PLA, 15 g C30+, 30 g C30+,in 900 g in 900 g methylene methylene chloride chloride 7 12 g PBS A, 12g PBS A, 35.6 — 23.7 19.95 18 g PLA, 18 g PLA, 15 g C30+, 30 g C30+, in900 g in 900 g methylene methylene chloride chloride 8 15 g PBS A, 15 gPBS A, 29.81 — 19.92 11.91 15 g PLA, 15 g PLA, 15 g C30+, 30 g C30+, in900 g in 900 g methylene methylene chloride chloride

Table 2 shows that a mixed solvent approach improved the quality ofcoating significantly resulting in a much slower release. Examples 3-5show slower nitrogen release than Examples 1 and 2. Without being boundby theory, it is believed that the mixture containing various boilingpoint solvents helped in keeping the solution coating more uniformbefore evaporation. Further, it was also discovered that by thermalconditioning of the granule having a coating containing wax along withthe polymer results in an improved (i.e., slower) release rate (Table3). Without wishing to be bound by theory, this is due to the wax in theinterpenetrating domains flowing due to thermal conditioning thussealing the polymer from defects such as pinholes, cracks, etc. Waxwithin the coating as opposed to outside the coating (overcoat) alsolikely increases the hydrophobicity of the coating layer, thus reducingwater permeability.

Example 2

The materials used in Example 2 are described in Table 4.

TABLE 4 Component Chemical Description Source PBS Poly(butylenesuccinate) 1020MD Showa Denko PLA Poly(lactic acid) 2003D NatureworksChloroform Aldrich Toluene Aldrich Urea Granular SABIC

Formulations for the coatings are shown in Table 5.

TABLE 5 Solution 1 Solution 2 PLA PBS Chloroform Toluene PLA PBSChloroform Toluene Sample # (g) (g) (g) (g) (g) (g) (g) (g) 9 21 9 630270 9 21 630 270 10 21 9 630 270 9 21 630 270 11 21 9 450 450 9 21 450450 12 21 9 450 450 9 21 450 450 13 21 9 0 900 9 21 0 900 14 21 9 450450 9 21 450 450 15 21 9 450 450 9 21 450 450 16 21 9 450 450 9 21 450450 17 21 9 450 450 9 21 450 450 18 21 9 450 450 9 21 450 450 19 21 9450 450 9 21 450 450 20 21 9 450 450 9 21 450 450 21 21 9 450 450 9 21450 450 22 21 9 450 450 9 21 450 450 23 21 9 450 450 9 21 450 450 24 219 450 450 9 21 450 450 25 21 9 450 450 9 21 450 450 26 21 9 450 450 9 21450 450 27 21 9 450 450 9 21 450 450 28 21 9 450 450 9 21 450 450 29 219 450 450 9 21 450 450

The fertilizer granules were placed in a stainless steel pan, which wasthen placed in a forced-air convection oven set to a temperature of90-110° C. for up to 15 hours. At different time intervals up to 15hours, a small aliquot of approximately 5 grams of urea was collectedand SEM images taken. FIGS. 1A-4B show the differences in the surfaceafter pre-heating. After the urea was in the oven for a given timeframe, the urea was then spray coated in a rotating drum withbiopolymers that were dissolved in organic solvents. The solvent wasevaporated, leaving behind the coating material on the surface of thefertilizer granule. Once the coating was deposited, the samples wereagain placed in a stainless steel pan and placed in a forced-airconvection oven that is set to 70-90° C. for up to 15 hours to removeresidual solvent that remains on the coated fertilizer granule. After agiven time frame, approximately 5 grams of the coated fertilizer granulewas placed in 95 grams of deionized water at room temperature (19-25°C.) and the percent nitrogen (% N) release was measured using arefractometer after 24 hours.

Additional samples from each batch were tested for abrasion resistance.The abrasion resistance tests consisted of placing a number of equallysized stainless steel balls and 100 mL of the coated fertilizer into astainless steel drum having equally spaced flights. The drum was closedand then rotated at 30 revolutions per minute for 5 minutes. After 5minutes, the stainless steel balls were separated from the coatedfertilizer using a sieve at which point approximately 5 grams of theabraded coated urea was placed in 95 grams of deionized water at roomtemperature and the % N release was measured using a refractometer after24 hours. Although described herein with respect to a force-airconvection oven, other devices can be used, including, but not limitedto, disc dryers, drum dryers, paddle dryers, rotary dryers, conveyordryers, and/or fluid bed dryers.

Table 6 shows the % N release for before and after the abrasion testalong with the pre- and post-heat treatment. Temperatures are listed in° C. and time in hours.

TABLE 6 1-Day % N Release Post- Before After Before Pre-Heat Pre-HeatPost- Heat Abrasion Abrasion and After Sample # T Time Heat T Time TestTest Δ 9 None 0 70 15 21.06 55.49 34.43 10 None 0 70 15 28.04 51.1323.09 11 None 0 70 15 16.12 40.23 24.11 12 None 0 70 15 11.31 25.3114.00 13 None 0 70 15 29.47 67.62 38.15 17 None 0 70 15 19.39 65.9346.54 18 None 0 70 15 22.94 62.35 39.41 19 105 15 70 15 12.85 20.21 7.3620 105 15 70 15 16.04 20.12 4.08 21 105 15 70 15 6.11 8.09 1.98 22 10515 70 15 29.88 27.11 −2.77 23 105 15 70 15 19.18 24.02 4.84 24 105 15 7015 15.15 19.52 4.37 25 105 15 70 15 28.08 26.59 −1.49

As can be seen in FIGS. 1A-4B, the pre-treatment of a surface of thefertilizer granule provides a smoother surface of the fertilizergranule. FIGS. 1A, 2A, 3A, and 4 are at 500 times magnification, whileFIGS. 1B, 2B, 3B, and 4B are at 2,000 times magnification. FIGS. 1A and1B are the control sample with no pre-treatment. FIGS. 2A and 2B are asample after pre-heating for 5 hours. FIGS. 3A and 3B are the sample inFIGS. 2A and 2B after pre-heating for 10 hours. FIGS. 4A and 4B are thesample in FIGS. 2A and 2B after pre-heating for 15 hours. As can be seenin the figures, a smoother surface is achieved with the longer heating.FIGS. 1A-4B further demonstrate that the surface morphology of thefertilizer granule undergoes transformation after it is heated in theforced-air convection oven. The sample in FIGS. 1A and 1B, which was nottreated with heat, does not have a smooth surface compared to thesamples that were heated for a period of time in FIGS. 2A-4B.

This transformation also appears to affect the % N release observedafter the abrasion test after 34 hours as shown in Table 6. The % Nrelease between the before abrasion and after abrasion test variesbetween 14.00% and 46.54% for samples that were not pre-heated. The % Nrelease difference between samples that were pre-heated varies from nochange to 7.36%.

The samples in Table 7 were also measured for % N release after 7 daysand the percent weight loss after post-heat treatment.

TABLE 7 Pre-Heat Pre-Heat % N Release Post-Heat Post-Heat % Wt. Sample #T Time 1 day 7 days T Time Loss 14 None 0 21.36 81.62 70 15 0.40 15 None0 18.90 77.00 70 15 0.37 16 None 0 19.78 79.09 70 15 0.24 26 105 1525.87 69.00 70 15 0.06 27 105 15 18.58 69.29 70 15 0.10 28 105 15 13.5565.18 70 15 0.10 29 105 15 17.86 56.26 70 15 0.06

As shown in Table 7, the samples that were pre-heated had asignificantly lower % N release after 7 days as compared to thenon-pre-heated samples. Furthermore, the post-heated (i.e., dried)samples which contained the pre-heated fertilizer granules after a 2%coating was applied had a significantly lower % weight loss as comparedto the post-heated samples without the pre-heated fertilizer granule.

Embodiment 1: A coated fertilizer, comprising: a fertilizer granule; anda coating disposed on a surface of the fertilizer granule, wherein thecoating comprises interpenetrating domains comprising polymer domainsand wax domains.

Embodiment 2: The coated fertilizer of Embodiment 1, wherein thefertilizer granule comprises urea.

Embodiment 3: The coated fertilizer of Embodiment 1 or Embodiment 2,wherein the fertilizer granule is a pre-treated fertilizer granulehaving improved adherence properties to the coating.

Embodiment 4: The coated fertilizer of any of Embodiments 1-3, whereinthe pre-treated fertilizer granule comprises a smoothed surface.

Embodiment 5: The coated fertilizer of any of Embodiments 1-4, whereinthe polymer domains comprise at least two polymers.

Embodiment 6: The coated fertilizer of any of Embodiments 1-5, whereinthe polymer domains comprise a biopolymer.

Embodiment 7: The coated fertilizer of Embodiment 6, wherein thebiopolymer is a polysaccharide, a polyester, lignin or a combinationcomprising at least one of the foregoing.

Embodiment 8: The coated fertilizer of any of Embodiments 1-7, whereinthe wax domains comprise a C₅-C₃₅ wax.

Embodiment 9: The coated fertilizer of any of Embodiments 1-8, whereinthe polymer domains have a first rate of biodegradation and the waxdomains have a second rate of biodegradation that differs from the firstrate under the same conditions.

Embodiment 10: The coated fertilizer of Embodiment 9, wherein thepolymer domains comprise at least two polymers, each having a differentrate of biodegradation under the same conditions.

Embodiment 11: The coated fertilizer of any of Embodiments 3-10, whereinthe pre-treated fertilizer granule has a percent nitrogen release after7 days of less than or equal to 70%, preferably, less than or equal to65%, more preferably, less than or equal to 60%.

Embodiment 12: A process of manufacturing the coated fertilizer of anyof Embodiments 1-11, comprising: at least partially dissolving a polymerand a wax in an organic solvent to form a coating composition;contacting the coating composition with a plurality of fertilizergranules to form at least partially coated fertilizer granules;evaporating the organic solvent from the at least partially coatedfertilizer granules to form dried at least partially coated fertilizergranules; and heating the dried at least partially coated fertilizergranules at a temperature effective to at least partially melt the waxto form a coating comprising interpenetrating domains comprising polymerdomains and wax domains.

Embodiment 13: The process of Embodiment 12, wherein the coatingcomposition further comprises an additional polymer.

Embodiment 14: The process of Embodiment 12 or Embodiment 13, furthercomprising forming an additional coating composition free of waxcomprising the polymers and organic solvent of the coating compositionand wherein the plurality of fertilizer granules is also contacted withthe additional coating composition prior to evaporating the organicsolvent.

Embodiment 15: The process of Embodiment 14, wherein the coatingcomposition and the additional coating composition comprise the polymersin differing amounts.

Embodiment 16: The process of Embodiment 13, further comprising formingan additional coating composition having the same components as thecoating composition and the wax is present in the additional coatingcomposition in an amount different from the coating composition andwherein the plurality of fertilizer granules is also contacted with theadditional coating composition prior to evaporating the organic solvent.

Embodiment 17: The process of any of Embodiments 12-16, furthercomprising applying additional wax while heating the dried at leastpartially coated fertilizer granules at a temperature effective to atleast partially melt the wax.

Embodiment 18: The process of any of Embodiments 12-17, wherein theorganic solvent comprises a combination comprising at least two organicsolvents, each having a different boiling point.

Embodiment 19: The process of any of Embodiments 12-18, wherein theorganic solvent comprises chloroform, toluene, methylene chloride, or acombination comprising at least one of the foregoing.

Embodiment 20: A process of manufacturing the coated fertilizer of anyof Embodiments 1-11, comprising: at least partially dissolving a firststructural polymer in a first solvent having a first boiling point toform a first solution; at least partially dissolving a second polymerand a wax in a second solvent having a second boiling point to form asecond solution, wherein the second boiling point is different from thefirst boiling point; contacting the first solution and the secondsolution with a plurality of fertilizer granules to form at leastpartially coated fertilizer granules; evaporating the first solvent andthe second solvent from the at least partially coated fertilizergranules to form dried at least partially coated fertilizer granules;and heating the dried at least partially coated fertilizer granules at atemperature effective to at least partially melt the wax to form acoating comprising interpenetrating domains comprising polymer domainsand wax domains.

Embodiment 21: The process of any of Embodiments 12-20, wherein thetemperature effective to at least partially melt the wax is 30 ° C. to130° C.

Embodiment 22: The process of any of Embodiment 12-21, furthercomprising using a rotating drum to contact the coating on thefertilizer granule.

Embodiment 23: The process of any of Embodiments 12-22, furthercomprising adding additional amounts of wax during heating the dried atleast partially coated fertilizer granules.

Embodiment 24: The process of any of Embodiments 12-23, furthercomprising pre-treating the fertilizer granule by heating to atemperature greater than or equal to 90° C., for a time period ofgreater than or equal to 5 hours.

The singular forms “a,” “an,” and “the” include plural referents unlessthe context clearly dictates otherwise. “Or” means “and/or.” Theendpoints of all ranges directed to the same component or property areinclusive and independently combinable. The suffix “(s)” as used hereinis intended to include both the singular and the plural of the term thatit modifies, thereby including at least one of that term (e.g.,“colorant(s)” includes at least one colorant). “Optional” or“optionally” means that the subsequently described event or circumstancecan or cannot occur, and that the description includes instances wherethe event occurs and instances where it does not. Unless definedotherwise, technical and scientific terms used herein have the samemeaning as is commonly understood by one of skill in the art to whichthis invention belongs. Substantially as described herein generallyrefers to greater than or equal to 75%, for example, greater than orequal to 75%, for example, greater than or equal to 95%.

As used herein, a “combination” is inclusive of blends, mixtures,alloys, reaction products, and the like. Compounds are described usingstandard nomenclature. For example, any position not substituted by anyindicated group is understood to have its valency filled by a bond asindicated, or a hydrogen atom. A dash (“-”) that is not between twoletters or symbols is used to indicate a point of attachment for asubstituent. For example, —CHO is attached through carbon of thecarbonyl group.

All references cited herein are incorporated by reference in theirentirety. While typical embodiments have been set forth for the purposeof illustration, the foregoing descriptions should not be deemed to be alimitation on the scope herein. Accordingly, various modifications,adaptations, and alternatives can occur to one skilled in the artwithout departing from the spirit and scope herein.

1. A coated fertilizer, comprising: a fertilizer granule; and a coatingdisposed on a surface of the fertilizer granule, wherein the coatingcomprises interpenetrating domains comprising polymer domains and waxdomains.
 2. The coated fertilizer of claim 1, wherein the fertilizergranule comprises urea.
 3. The coated fertilizer of claim 1, wherein thefertilizer granule is a pre-treated fertilizer granule having improvedadherence properties to the coating.
 4. The coated fertilizer of claim3, wherein the pre-treated fertilizer granule comprises a smoothedsurface.
 5. The coated fertilizer of claim 1, wherein the polymerdomains comprise at least two polymers.
 6. The coated fertilizer ofclaim 1, wherein the polymer domains comprise a biopolymer.
 7. Thecoated fertilizer of claim 1, wherein the wax domains comprise a C₅-C₃₅wax.
 8. The coated fertilizer of claim 1, wherein the polymer domainshave a first rate of biodegradation and the wax domains have a secondrate of biodegradation that differs from the first rate under the sameconditions.
 9. The coated fertilizer of claim 8, wherein the polymerdomains comprise at least two polymers, each having a different rate ofbiodegradation under the same conditions.
 10. The coated fertilizer ofclaim 3, wherein the pre-treated fertilizer granule has a percentnitrogen release after 7 days of less than or equal to 70%.
 11. Aprocess of manufacturing coated coated fertilizer comprising afertilizer granule and a coating disposed on a surface of the fertilizergranule, wherein the coating comprises interpenetrating domainscomprising polymer domains and wax domains, the process comprising: atleast partially dissolving a polymer and a wax in an organic solvent toform a coating composition; contacting the coating composition with aplurality of fertilizer granules to form at least partially coatedfertilizer granules; evaporating the organic solvent from the at leastpartially coated fertilizer granules to form dried at least partiallycoated fertilizer granules; and heating the dried at least partiallycoated fertilizer granules at a temperature effective to at leastpartially melt the wax to form a coating comprising interpenetratingdomains comprising polymer domains and wax domains.
 12. The process ofclaim 11, wherein the coating composition further comprises anadditional polymer.
 13. The process of claim 12, further comprisingforming an additional coating composition free of wax comprising thepolymers and organic solvent of the coating composition and wherein theplurality of fertilizer granules is also contacted with the additionalcoating composition prior to evaporating the organic solvent, whereinthe coating composition and the additional coating composition comprisethe polymers in differing amounts.
 14. The process of claim 12, furthercomprising forming an additional coating composition having the samecomponents as the coating composition and the wax is present in theadditional coating composition in an amount different from the coatingcomposition and wherein the plurality of fertilizer granules is alsocontacted with the additional coating composition prior to evaporatingthe organic solvent.
 15. The process of claim 11 further comprisingapplying additional wax while heating the dried at least partiallycoated fertilizer granules at a temperature effective to at leastpartially melt the wax.
 16. A process of manufacturing a coatedfertilizer comprising a fertilizer granule and a coating disposed on asurface of the fertilizer granule, wherein the coating comprisesinterpenetrating domains comprising polymer domains and wax domains, theprocess comprising: at least partially dissolving a first structuralpolymer in a first solvent having a first boiling point to form a firstsolution; at least partially dissolving a second polymer and a wax in asecond solvent having a second boiling point to form a second solution,wherein the second boiling point is different from the first boilingpoint; contacting the first solution and the second solution with aplurality of fertilizer granules to form at least partially coatedfertilizer granules; evaporating the first solvent and the secondsolvent from the at least partially coated fertilizer granules to formdried at least partially coated fertilizer granules; and heating thedried at least partially coated fertilizer granules at a temperatureeffective to at least partially melt the wax to form a coatingcomprising interpenetrating domains comprising polymer domains and waxdomains.
 17. The process of claim 11, wherein the temperature effectiveto at least partially melt the wax is 30° C. to 130° C.
 18. The processof claim 11, further comprising using a rotating drum to contact thecoating on the fertilizer granule.
 19. The process of claim 11, furthercomprising adding additional amounts of wax during heating the dried atleast partially coated fertilizer granules.
 20. The process of claim 11,further comprising pre-treating the fertilizer granule by heating to atemperature greater than or equal to 90° C., for a time period ofgreater than or equal to 5 hours.